Answer:

use formula an= a+(n-1)d

where a is the first term

d= common difference

an = nth term

this formula for finding A P

for sum of n terms= sn = a(n/2+1)d

Verified answer

The common difference of the AP is 4.

Explanation:

As per given , we have

last term= 119

8th term from the end =91

Since the AP is starting from the end , let a = 119 and d= common difference for the given arithmetic progression from the end.

Since nth term = a+(n-1)d

It means 8th term from the end : 119+(8-1)d= 91119+(8−1)d=91

\begin{gathered}119+7d=91\\\\ 7d= 91-119\\\\ 7d= -28\\\\ d=\dfrac{-28}{7}=-4\end{gathered}

119+7d=91

7d=91−119

7d=−28

d=

7

−28

=−4

Now , the common difference of the AP is -d = -(-4) = 4

Hence, the common difference of the AP is 4.